gluBuild2DMipmapLevels Subroutine

OpenGL 1.2 for AIX: Reference Manual

gluBuild2DMipmapLevels Subroutine

Purpose

Builds a subset of 2D mipmap levels.

Library

OpenGL C bindings library: libGL.a

C Syntax

GLint	gluBuild2DMipmapLevels( GLenum target,
   GLint internalFormat,
   GLsizei width,
   GLsizei height,
   GLenum format,
   GLenum type,
   GLint level,
   GLint base,
   GLint max,
   const void *data )

Description

gluBuild2DMipmapLevels builds a subset of prefiltered 2D texture maps of decreasing resolutions called a mipmap. This is used for the antialiasing of texture mapped primitives.

A return value of 0 indicates success, otherwise a GLU error code is returned (see gluErrorString).

A series of mipmap levels from base to max is built by decimating data in half along both dimensions until size 1x1 is reached. At each level, each texel in the halved mipmap level is an average of the corresponding four texels in the larger mipmap level. (In the case of rectangular images, the decimation will ultimately reach an N x 1 or 1 x N configuration. Here, two texels are averaged instead.) glTexImage2D is called to load these mipmap levels from base to max. If max is larger than the highest mipmap level for the texture of the specified size, then a GLU error code is returned (see gluErrorString) and nothing is loaded.

For example, if level is 2 and width is 16 and height is 8, the following levels are possible: 16x8, 8x4, 4x2, 2x1, 1x1. These correspond to levels 2 through 6 respectively. If base is 3 and max is 5, then only mipmap levels 8x4, 4x2 and 2x1 are loaded. However, if max is 7 then an error is returned and nothing is loaded since max is larger than the highest mipmap level which is, in this case, 6.

The highest mipmap level can be derived from the formula log2(max(width,height)*(2^level)).

See the glTexImage1D subroutine for a description of the acceptable values for format parameter. See the glDrawPixels subroutine for a description of the acceptable values for type parameter.

Parameters

target	Specifies the target texture. Must be GL_TEXTURE_2D.
internalFormat	Requests the internal storage format of the texture image. Must be 1, 2, 3, or 4 or one of the following symbolic constants: GL_ALPHA GL_ALPHA4 GL_ALPHA8 GL_ALPHA12 GL_ALPHA16 GL_LUMINANCE GL_LUMINANCE4 GL_LUMINANCE8 GL_LUMINANCE12 GL_LUMINANCE16 GL_LUMINANCE_ALPHA GL_LUMINANCE4_ALPHA4 GL_LUMINANCE6_ALPHA2 GL_LUMINANCE8_ALPHA8 GL_LUMINANCE12_ALPHA4 GL_LUMINANCE12_ALPHA12 GL_LUMINANCE16_ALPHA16 GL_INTENSITY GL_INTENSITY4 GL_INTENSITY8 GL_INTENSITY12 GL_INTENSITY16 GL_RGB GL_R3_G3_B2 GL_RGB4 GL_RGB5 GL_RGB8 GL_RGB10 GL_RGB12 GL_RGB16 GL_RGBA GL_RGBA2 GL_RGBA4 GL_RGB5_A1 GL_RGBA8 GL_RGB10_A2 GL_RGBA12 GL_RGBA16
width, height	Specifies the width and height, respectively, in pixels of the texture image. These should be a power of 2.
format	Specifies the format of the pixel data. Must be one of: GL_COLOR_INDEX GL_DEPTH_COMPONENT GL_RED GL_GREEN GL_BLUE GL_ALPHA GL_RGB GL_RGBA GL_BGRA GL_LUMINANCE GL_LUMINANCE_ALPHA
type	Specifies the data type for data. Must be one of: GL_UNSIGNED_BYTE GL_BYTE GL_BITMAP GL_UNSIGNED_SHORT GL_SHORT GL_UNSIGNED_INT GL_INT GL_FLOAT GL_UNSIGNED_BYTE_3_3_2 GL_UNSIGNED_BYTE_2_3_3_REV GL_UNSIGNED_SHORT_5_6_5 GL_UNSIGNED_SHORT_5_6_5_REV GL_UNSIGNED_SHORT_4_4_4_4 GL_UNSIGNED_SHORT_4_4_4_4_REV GL_UNSIGNED_SHORT_5_5_5_1 GL_UNSIGNED_SHORT_1_5_5_5_REV GL_UNSIGNED_INT_8_8_8_8 GL_UNSIGNED_INT_8_8_8_8_REV GL_UNSIGNED_INT_10_10_10_2 GL_UNSIGNED_INT_2_10_10_10_REV
level	Specifies the mipmap level of the image data.
base	Specifies the minimum mipmap level to pass to glTexImage2D.
max	Specifies the maximum mipmap level to pass to glTexImage2D.
data	Specifies a pointer to the image data in memory.

Error Codes

GLU_INVALID_VALUE is returned if level > base, base < 0, max < base or max is > the highest mipmap level for data.

GLU_INVALID_VALUE is returned if width or height are < 1.

GLU_INVALID_ENUM is returned if internalFormat, format or type are not legal.

GLU_INVALID_OPERATION is returned if type is GL_UNSIGNED_BYTE_3_3_2 or GL_UNSIGNED_BYTE_2_3_3_REV and format is not GL_RGB.

GLU_INVALID_OPERATION is returned if type is GL_UNSIGNED_SHORT_5_6_5 or GL_UNSIGNED_SHORT_5_6_5_REV and format is not GL_RGB.

GLU_INVALID_OPERATION is returned if type is GL_UNSIGNED_SHORT_4_4_4_4 or GL_UNSIGNED_SHORT_4_4_4_4_REV and format is neither GL_RGBA nor GL_BGRA.

GLU_INVALID_OPERATION is returned if type is GL_UNSIGNED_SHORT_5_5_5_1 or GL_UNSIGNED_SHORT_1_5_5_5_REV and format is neither GL_RGBA nor GL_BGRA.

GLU_INVALID_OPERATION is returned if type is GL_UNSIGNED_INT_8_8_8_8 or GL_UNSIGNED_INT_8_8_8_8_REV and format is neither GL_RGBA nor GL_BGRA.

GLU_INVALID_OPERATION is returned if type is GL_UNSIGNED_INT_10_10_10_2 or GL_UNSIGNED_INT_2_10_10_10_REV and format is neither GL_RGBA nor GL_BGRA.

Files

/usr/include/GL/gl.h

Contains C language constraints, variable type definitions, and ANSI function prototypes for OpenGL.

Related Information

The glDrawPixels subroutine, glTexImage1D subroutine, glTexImage2D subroutine, glTexImage3D subroutine, gluBuild1DMipmaps subroutine, gluBuild2DMipmaps subroutine, gluBuild3DMipmaps subroutine, gluErrorString subroutine, glGetTexImage subroutine, glGetTexLevelParameter subroutine, gluBuild1DMipmapLevels subroutine, gluBuild3DMipmapLevels subroutine.